It is known that providing a supply of oxygen to a wound to or through the skin (e.g., ulcers, abrasions, cuts, sores, etc.) promotes healing of the wound. Oxygen therapy is used for inducing the growth of new skin tissue to close and heal ischemic wounds. Topical oxygen therapy calls for applying oxygen directly to an open wound. The oxygen dissolves in tissue fluids and improves the oxygen content of the intercellular fluids. Injuries and disorders which may be treated with topical oxygen include osteomylelitis, tendon and cartilage repair, sprains, fractures, burns and scalds, necrotizing fasciitis, pyoderma gangrenosum, refractory ulcers, diabetic foot ulcers and decubitus ulcers (bed sores) as well as cuts, abrasions, and surgically induced wounds or incisions.
In light of the documented benefits of such oxygen therapy, there have been several proposed methods for providing such an oxygen supply to a wound or regulating the oxygen concentration in the vicinity of a wound while also preventing contamination of the oxygen supply from the wound. Prior art teaches the application of topical hyperbaric oxygen by placing the entire affected limb of a person in a sealed chamber that features controlled pressure sealing and automatic oxygen regulation control. Not only are such oxygen chambers expensive and difficult to sterilize, however, they are also cumbersome in that the chamber must be hooked up to an external oxygen tank, limiting the patient's mobility. In addition, because the entire limb is placed in a chamber or bag, large areas of skin may be unnecessarily subjected to high levels of oxygen. Such high levels of oxygen present risks of vasoconstriction, toxicity and tissue destruction. U.S. Pat. No. 4,328,799 to LoPiano describes such a system in which a recumbent patient is connected to a gas chamber attached to an oxygen supply.
U.S. Pat. Nos. 5,578,022 and 5,788,682 describe systems in which oxygen producing devices are incorporated into a patch or bandage which is placed directly over a wound. Both these patents describe devices in which oxygen is produced electrochemically and transported across an ion conductive membrane. In such membranes, water typically provides a hydrogen bonding network and enables the rapid movement of protons through the membrane necessary for oxygen production in such a system. Water, however, has a relatively high vapor pressure and will evaporate. As water in the membrane evaporates, the membrane loses its ability to effectively conduct ions. Thus, over the course of several days, membranes used in such devices tend to lose their ability to transport oxygen. Attempting to keep the membrane hydrated can result in complications. For example, the inclusion of a water source to keep the membrane moist can make the device cumbersome, mitigating one of the key benefits of such a device. In addition, water presents a potential breeding ground for microbes. This is highly undesirable in such an oxygen generating device, which is often placed on or near open wounds that are susceptible to microbial infection.
Therefore, a need exists for a convenient and inexpensive means of maintaining the ionic conductivity of the membrane in such electrochemical oxygen producing devices over an extended period of time.